Electrodynamic speaker



Jan. 23, 1934. H TENNY ELEQTRODYNAMIC SPEAKER Original Filed May 27, 1930 0A -I/INVENTOR.

Patented Jan. 23, 1934 nausea ELECTRODYNAMIC SPEAKER Henry 55. Tenny, Oakland, Ca-iii, assignor to The Rola Company, ration oi @hio leveland, Ohio, a corpo- Application may 27, 1 30. Serial No. 456,115 Renewed April 8, 1933 '2 Claims.

The invention is for an electro-dynamic speaker or sound translating device.

The main object of the invention is to provide a sound translating device of the dynamic type '5 in which the impressed sound waves are capable of being delivered true to form and frequency practically throughout the range of audibility, without the imposition of stray vibrations due to an eccentric air gap.

Another object of the invention is to so construct the magnetic core as to permit precision adjustment of the air gap at the time of as sembling the constituent parts whereby the voice coil is caused to float in a truly concentric air p- A further object of the invention is to construct the cone so as to enable precision centering of the voice coil in the air gap and fixing the coil in position by means of an adjustable spider and screws, which screws are accessible through apertures in the cone or membrane, whose natural period is beyond the range of audibility.

Other objects of the invention will be apparent when the following description read on the drawing forming a part of this specification.

The invention consists primarily of an electrodynainic speaker having a magnetic core so constructed as to permit accurate adjustment of the air gap and voice coil, the cone having apertures through which the voice coil spider screws may be tightened after the voice coil is centered, and, having an intermediately tapped field coil.

.,eferring to the accompanying drawing Fig. 1 is a front elevation of the cone and supporting frame showing the apertures in the cone, and the voice coil connections;

Fig. 2 is a part sectional side elevation showing the spider screws and cone apertures as relatec to the speaker;

Fig. 3 is a fragmentary view indicating the coupling transformer and a portion of the speaker field, and terminals block;

Fig. -l is a plan View of the voice coil spider;

Fig. 5 is an elevation of the voice coil.

The field coil 6 consists of a multiplicity of turns of insulated wire having end terminals 7 and 8 and an intermediate tap 8 connected by means of the leads 1D, 11 and 12, the coil being wound on a spool or in spool form for 50 readily mounting over the magnetic core 13, which is fixed in the U shapes magnetic 14, a magnetic plate 15 being attached by means of screws 15 through enlarged holes in the f anges 1'7, to the U shaped frame 14, providing r by a closed magnetic field. The plate a central aperture 18 which is concentrically disposed relative to the core 13 by means of a spacer ring which is removed after tightening the screws 16. The space between the walls of aperture 18 and core 13 provide an air gap in (Cl. Nil- 1155) Wii' 1; the voice coil 19 is fioatably mounted. re voice coil 19 consists of an insulating form 21% having a plurality of turns of insulated wire 21 wound thereon, the ends 22 and 23 providterrninals which. connected to the respective terminals of a coupling transformer. A collar 24 provides a shoulder for mounting of the voice coil spider and cone, the insulating form 20 being slit axially at a plurality of points as at to'permit cementing to the inner surface of the cone as at 26, the separate tabs being bent back, after insertion through an aperture at the apex of the cone.

The voice coil spider, Fig. 4, is made of a nonmagnetic resilient material such as spring brass, and is so formed as to provide long life, and, when assembled to the voice coil, a natural period of vibration substantially equal to the natural period of the cone, the collar 27 being conical in form conforming to the slope of the'conc, the aperture 28 receiving the end of the form 20 and seating against the shoulder 29 on the collar 24. A recess 30 clears the terminals 22 and 23 on the voice coil. The mounting apertures 31 are made suificiently large to permit sufficient adjustment to accurately center the voice coil 19 in the air gap. The supporting arms 32 are of special form, the inner edge being substantially concentric with the collar 2'7, the outer edge comprising a compound curve, no portion of which is concentric with the collar 2'7, the inner edges of the arms being diametrically opposed relative to the center of the aperture 28, the outer edge increasing in width to point of connection with the collar 27. The voice coil spider is mounted by means of screws 33 through apertures 31 to posts 34. integral with the magnetic plate 15.

The cone consists of a sheet of parchment or membrane 35 formed to conical shape with the apex removed, through which the insulating form slitted end 20 is inserted, the tabs being bent back and cemented as at 26. Attached to the base of the cone is flexible material or membrane 36 with substantially zero period of vibration for supporting the cone at the outer edge. Apertures are provided in the cone at 3'7, through which the screws 33 may be conveniently adjusted. The terminals 22 and 23 of the voice coil are connected to eyelets 38, fixed in the cone.

The speaker frame or support consists of a comically formed spider having a ring base 39 with integral ears ii) having mounting holes 41 therein, the body consistingof a plurality of integral arms :2 terminatin in a base 43 to which is attached the U shaped magnetic member 115 14. with interposed late 15. An aperture is provided in the base 43 to clear the voice coil spider Fig. 4. A plurality of apertures are provided in the ring base, and registering apertures in the membrane 36 and holding ring 44, rivets 45 fixedly 120 securing the assembly and retaining the membrane 36 in fixed position, and permitting axial movement of the cone and voice coil.

Fixed to one of the arms 42 is a coupling transformer 43' having a primary and a secondary winding, and primary winding leads 44 and 45' and secondary winding leads 46 and 47.

The terminal block consists of a section of insulating material fixed to the inside of arm 42 adjacent the coupling transformer 43 and provided with a plurality of terminals '7, 8, 9, l8 and 49, for connection in a radio circuit.

The connections to the various terminals are as follows: The primary terminals 48 and 49 are connected respectively to the plate of a power tube and the high potential positive or heater circuit of a rectifier tube. The secondary leads 46 and l? are connected to the voice coil leads 22 and 23 through the eyelets 38. The field coil 6 has its opposite terminals 7 and 8 connected respectively to negative potential and ground or zero potential, the negative potential being obtained from a center tap on the high potential or rectifier tube plate winding or equivalent sources. The intermediate tap 12 is connected through a resistance capacity filter and an input coupling to the grid of the power tube.

Other methods of hooking up may be used although the hcolrup as outlined above has given exceptional results as to tone quality and free dom from hum. This hookup is the subject of a copending application. One method as common- 1y practiced comprises connecting the plate of the power tube to one primary terminal 48 of the coupling transformer 43, the other primary terminal 49 being connected to a filter condenser and to the field terminal '2, the other field terminal 8 being connected to another filter condenser and high potential positive or heater circuit of a rectifier tube, consisting, in the order named, of a series hookup of power tube anode, coupling transformer primary, field coil and rectifier tube cathode, the intermediate tap 9 being left open.

It will be noted that changes may be made in construction and arrangement of parts which are consistent with the scope of the appended claims and that such variations will not detract from the scope and advantages of the invention.

I am aware that radio loud speakers of the cone and electro-dynamic type have been made therefore I do not claim such a device broadly, but I do claim:

1. In combination with an electro-dynamic sound translating device having a cone diaphragm, a voice coil spider and mounting screws therefor; apertures formed in said diaphragm in registry with said voice coil spider mounting screws for permitting adjustment of said voice coil after assembly of the device.

2. In combination with an electro-dynamic sound translating device provided with a cone diaphragm and a voice coil; voice coil centering means comprising a resilient adjustable spider having the voice coil secured therein, and mounting screws therefor and diametrically disposed apertures in said cone in registry with mounting screws for said spider for conveniently and accurately adjusting said voice coil in the voice coil air gap.

3. In combination with an electro-dynamic sound translating device having a diaphragm, a field coil and a magnetizable core. an air gap concentric of said core, and a voice coil axially floatable in said air gap and fixed centrally of said diaphragm; voice coil mounting means comprising an adjustable spider, said spider being adjustably mounted by means of screws and apertures provided in said diaphragm through which access is obtained to said screws.

4. An electro-dynamic sound translating device comprising a magnetic core and field path, a dynamic field coil provided with an intermediate tap adapted to provide bias potential for circuit control, a resilient non-magnetic spider, a conical diaphragm, an air gap concentric with one end of said core, a voice coil axially floatable in said air gap, said resilient non-magnetic spider being adjustably mounted relative to said magnetic field path, and apertures provided in said diaphragm adapted to register with mounting screws for said spider through which access to said screws is provided.

5. An electro-dynamic sound translating device comprising a U shaped magnetic field path having a core fixed in the transverse member thereof, and centrally disposed relative to the legs thereof, a magnetic plate adjustably fixed to the legs thereof and having an aperture concentric to said core providing an air gap, a resilient non-magnetic spider, a voice coil axially floatable in said air gap and fixed in said resilient non-magnetic spider, said spider being adjustably attached to said magnetic plate, mounting screws for said spider, a conical diaphragm fixed to said voice coil, and apertures provided in said diaphragm in registry with and adapted to provide access to said spider mounting screws.

6. An electro-dynamic sound translating device comprising, in combination with a magnetizable core, a field coil, a diaphragm supporting frame and a voice coil, a voice coil spider having a central aperture for said voice coil and a recess for passage of the voice coil lead wires, a pair of arms, the inner ends of which are diametrically disposed radially, curving into a concentric inner edge, the outer edge being non-concentric and comprising a compound curve, and apertures adjacent the ends of said arms adapted to adjustably receive mounting screws, and a conical diaphragm provided with apertures through which direct access is gained to said mounting screws.

'7. An electro-dynamic sound translating de vice comprising, in combination with a magnetizable field path and core and a concentric air gap about one end of said core; an intermediately tapped field winding on said core adapted to provide bias potential, a spider, a conical diaphragm, a voice coil fixed in said spider and to said diaphragm, said spider consisting of a central ring with concentric voice coil receiving aperture and a voice coil terminal receiving recess, supporting arms integral with said ring and extending substantially concentric through arcs of approximately ninety degrees, mounting holes adjacent the ends of said arms and mounting screws therefor, said mounting holes permitting adjustment of said voice coil in said air gap, said diaphragm being provided with apertures in registry with said mounting screws in said mounting holes whereby adjustment of the voice coil in the air gap may be performed after assembly of the device.

l HENRY S. TENNY. 

